1. Field of the Invention
The present invention relates to solenoid operated air flow control valves, the solenoid moving a valve seal from a valve seat. A passageway between an air supply and an air destination through the valve is opened or closed by movement of the valve seal. More particularly, the invention relates to valves wherein a valve stem carrying the valve seal thereon is formed of magnetic material and defines an armature upon which an electromagnetic field induced by the solenoid energizing a coil opens the valve. Such valves often include mechanisms including multiple diaphragms, pistons and the like for balancing the pressure within the valve tending to hold the valve seal in a closed position against the valve seat. The present invention is related to this type of valve to the extent that it is contemplated that the internal pressure of the valve is balanced to thereby minimize the electrical power necessary to move the valve stem armature and attached valve seal to open the valve.
2. Description of the Prior Art
Several prior art patent references show a solenoid operated valve including structure for balancing pressures within the valve to minimize the electrical power necessary to open or close the valve. A balanced valve using two diaphragms is seen in G. Paulsen, U.S. Pat. No. 3,985,333; G. Wolfslau et al, U.S. Pat. No. 2,826,215; and C. Cole, U.S. Pat. No. 2,875,784.
More specifically, the Paulsen patent reference shows two diaphragms, each of equal area to the valve seat area, the net force acting to open or close the valve being equal because the same pressure is acting on one of the diaphragms and the valve seat. Paulsen uses a coil to actuate a valve stem or armature made of magnetic material. The concept of Paulsen is to balance the pressure on an inlet side of the valve seat with one of the diaphragms and on an outlet side of the valve seat with the other of the diaphragms. Wolfslau et al also use two selectively positioned diaphragms, one on the outlet side and one on the inlet side of the valve seat. The armature of Wolfslau is not integral with the valve stem, but rather is slideable with respect thereto.
Cole is a three-way valve operated by a solenoid, two outlets are present in Cole, rather than the one of the two-way valves exemplified by Paulsen and Wolfslau. An integral stem of Cole connects a pair of valve heads or seals intermediate a pair of diaphragms also connected to the stem. The stem moves along a longitudinal axis of a valve body. One of the valve seats has a surface area equal to one of the diaphragms and is balanced with respect to one valve position. The other diaphragm associated with the other valve seat has a greater area than the corresponding valve seat and is used in conjunction with a supply of pressurized air to move the entire valve stem from a balanced configuration.
Other solenoid operated valves include balancing mechanisms other than diaphragms. J. Kenann, U.S. Pat. No. 2,934,090, uses two pistons in a three-way valve to obtain balanced operation. J. Collins, U.S. Pat. No. 2,893,428, uses a uniquely configured multiple surface valve spool in association with a piston to obtain balanced operation.
Manually or motor operated valves with balancing also include multiple structural components to achieve a balanced configuration in one or more valve positions. L. Lindsay, U.S. Pat. No. 2,682,386, utilizes a bellows in combination with a piston to balance a valve. C. Peters et al, U.S. Pat. No. 2,897,836, is a three-way valve utilizing a diaphragm and piston to achieve a balanced valve. M. Freeman, U.S. Pat. No. 3,063,469 utilizes two separate diaphragms, as well as additional structure to obtain a balanced operating mode.
The problem presented by many of the references is one of simplicity and ease of operation. For example, the patent to Lindsay is a three-way valve wherein the internal pressure in a bellows is balanced with a diaphragm-like arrangement. The valve seat area in Lindsay is not balanced by any equal area structure, though patents such as Paulsen, even though including two diaphragms, do balance by equaling the valve seat area to a diaphragm area. Many of the patent references, for example Paulsen, use a multiple component balancing structure to obtain a valve balanced in the closed position. To open the valve, a solenoid needs to overcome a spring force. It is the nature of Paulsen, as well as Wolfslau, to balance forces either side of the valve seat, in both the open and closed valve positions, by using the two diaphragms.
A manually actuated valve that uses a single deformable structure connected to a valve stem operably connected to a valve seal, which structure achieves balanced operation is seen in W. Fulton, U.S. Pat. No. 1,153,681. The diameter of the bellows structure in Fulton is essentially the same as the valve seat diameter, and the effective areas are therefore equal. The downstream or outlet side of the valve is placed in communication with an outer surface of the bellows, resulting in balanced forces on the area of the valve seal circumscribed by the valve seat. Compressing the bellows through use of a valve lever decreases its effective diameter and resulting force applied to the valve seal, helping reduce the force necessary to move the valve to the open position. Fulton does show the concept of communicating the outlet or downstream pressure of a valve seat with the inlet side which has deformable structure to establish a balanced operating position.